If there is anyone out there who doesn't have enough to be shocked about, you can bet your John Galliano that the fashion industry will find some way to offend them within the next five minutes. That's what fashion thrives on: subversion and irreverence; an immaculately groomed, sneering Johnny Rotten worth millions, the world's best-dressed troll.

The latest person to express outrage at this industry's flagrant disregard for common decency is the archbishop of Canterbury, Justin Welby, who writes in the foreword to his first Lent book that the crucifix has become a fashion statement, devoid of religious meaning. This from a man who regularly wears a dress made of gold.

To claim the cross as simply a Christian motif now is to exist in a vacuum. To express disappointment at the fact it has become just another bauble is to miss the point entirely, something the church has proved adept at for 2,000 years. When institutions insist on stasis, they become irrelevant. And when they do that in high dudgeon, they invite iconoclasm – something fashion has proved adept at for just as long.

People have worn crosses as decoration since Christ was taken down from his: just look at any Giotto frescoes or Renaissance dandy portraits. Devout, God-fearing people from a time when the cross meant everything – and when it was just as much of an ornament as it is now.

What Welby doesn't appear to realise is that the cross has more meaning now than it ever has done, thanks, in part, to its rehabilitation at the hands of what he calls "fashion", but what is actually just habit and custom. For many, the cross is a piece of jewellery you don't take off, rather than a trend. Before "fashion" made it ubiquitous, you mostly saw the cross on banners over the heads of knights sacking cities; before fashion, it was a symbol under which men and women were arbitrarily burned to death. We have evolved to wear crucifixes on necklaces without feeling the crushing weight of potential divine wrath and brimstone.

Now you see 14th-century-style devotional mosaics picked out in paillettes across a dress by Dolce & Gabbana, and Byzantine-style crosses inlaid on leather under the instructions of Donatella Versace. These mischievous Italian designers are working in the high Catholic mode, inspired by the opulence of the religion their country has grown up with. They weave religious imagery into their work, not to strip it of meaning but because it remains at the heart of their culture still. Not, perhaps, for its dogma, but for its iconography, its traditions, its teachings. And for its beauty.

The appropriation of the establishment into popular culture is nothing new. In the wake of the 60s and punk, we have no more hallowed icons to tiptoe around. It's a free-for-all. Look around and you'll see people walking about in T-shirts printed with CCCP or plastered with Che Guevara's face. Look further and you see people in faked approximations of designer logos – that they've been traduced doesn't detract from their meaning; it gives them a new story.

This is no bad thing. Once, people wore the cross for protection. Thankfully, we don't need to live by talismans and the evil eye any more: we have science. So our lingering affection for the cross is entirely symbolic. What Welby doesn't realise is that advertising execs would kill their firstborn to come up with something with such visual traction, something that needs no explanation and no translation.

The archbishop should reflect on the fact that religion must adapt to survive. We are a Christian culture, if not a Christian nation any more. That the cross no longer stands for exactly what it signified in the 13th century is logical. And it's a comfortable osmosis. I'd take trendy over tyranny any day.